Car-sized armoured glyptodonts turned out to be true armadillos
Glyptodonts were armadillos the size of a small car, up to 4 metres long and over two tonnes, sealed inside a rigid shell of hundreds of bony plates. Some swung spiked tail clubs like an ankylosaur's. They vanished about 12,000 years ago, possibly helped along by the first human hunters in the Americas.
The oldest widely accepted glyptodont fossils come from South America in the late Eocene, around 38 million years ago, with fuller skeletons from the Oligocene and Early Miocene onward. The group split early into two branches: one containing the famous Glyptodon and Glyptotherium, probably from northern South America, and a larger southern branch holding most of the diversity. After the Isthmus of Panama joined the continents about three million years ago, Glyptotherium walked north in the Great American Interchange, alongside ground sloths and other relatives.
For a long time glyptodonts were placed in a family of their own, and their link to living armadillos was disputed. In 2016 a study of the mitochondrial genome of Doedicurus showed it sat inside the modern armadillo family tree, closest to the fairy armadillos and the giant and three-banded armadillos. Most armadillos and the glyptodonts were then regrouped into a new family, Chlamyphoridae, though some researchers still use the old name. Their distinctive shell appears to have evolved from the banded armour of ordinary armadillos, and inner-ear anatomy points to the extinct pampatheres as close kin.
The biggest, such as Doedicurus, stood 1.5 metres tall. Armour up to 2.5 centimetres thick covered the back, the top of the head and even the underside, and the backbone was largely fused. Legs were short and stout, the skull short and blunt, and the grooved teeth kept growing throughout life. Rings of bone let the tail bend, and in many southern species it ended in a solid tube whose pits probably anchored horny spikes, making it a formidable weapon.
Glyptodonts died out abruptly at the close of the Late Pleistocene along with most large animals of the Americas. Evidence that newly arrived Paleoindians hunted them suggests people may have contributed to their disappearance.
Source: Glyptodont
